Undesired output (Levels) while selecting from R dataframe

Question

Part of my code is similar to following:

id.row <- c("x1","x2", "x10", "x20")
id.num <- c(1, 2, 10, 20)
id.name <- c("one","two","ten","twenty")
info.data <- data.frame(id.row, id.num, id.name)

req.mat <- matrix(1:4, nrow = 2, ncol = 2)
row.names(req.mat) <- c("x1","x10")

p1 <- info.data$id.row %in% row.names(req.mat)

op1 <- info.data$id.num[p1]
op2 <- info.data$id.name[p1]

I think the code is pretty much self explanatory and am getting the results that i want. There is no problem in printing op1 but when I am trying to get op2 its giving me additional output (Levels). As,there are 1000s of rows in original info.data so this "level" is not looking nice. Is there a way to turn it off?

The linked "duplicate" question is quite different from this one. This is asking how to not PRINT factors, the other is asking how to remove extra factor levels that are no longer used. — Josiah Yoder, Jul 05 '19 at 14:59

score 4 · Answer 1 · edited Mar 20 '17 at 14:54

4

Maybe you can use print(op2, max.levels=0)

edited Mar 20 '17 at 14:54

Uwe

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answered Mar 17 '17 at 18:08

Pablo

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This suggestion worked for me when printing a factor vector. – Uwe Mar 20 '17 at 14:55

score 0 · Answer 2 · answered Jun 10 '14 at 19:09

If you didn't want any of your variables to be factors, then

info.data <- data.frame(id.row, id.num, id.name, stringsAsFactors=F)

is a good choice. If you wanted id.row but not id.name to be a factor then

info.data <- data.frame(id.row=factor(id.row), id.num, id.name, 
    stringsAsFactors=F)

is better to set that up. If you created your data in some other way so they already exist as factors in the data.frame, you can convert them back to character with

info.data$id.name <- as.character(info.data$id.name)

If you do want id.name to be a factor but just want to drop the extra levels after subsetting, then

op2 <- info.data$id.name[p1, drop=T]

will do the trick.

Undesired output (Levels) while selecting from R dataframe

2 Answers2